The present invention relates to an air intake system for supplying the intake air and fuel to an internal combustion engine, and particularly to an air intake system for an internal combustion engine in which an intake assembly and independent intake pipes are provided along the passage of intake air to the cylinders of the engine.
Generally, an air intake system for an internal combustion engine is provided with an intake assembly, to which the air supplied from an air cleaner flows in accordance with the opening of a throttle valve, and independent intake pipes in which the air in the intake assembly is distributed to each cylinder of the internal combustion engine. In the intake system, the various members which constitute the intake system, such as an atmospheric pressure intake passage upstream of the throttle valve, a negative pressure intake passage or intake assembly on the down stream side of the throttle valve, independent intake pipes, etc., are connected in series. The intake system is relatively long, and so it has a disadvantage in that the utilization rate of the space in the engine compartment is low. In addition, the layout in the engine compartment is limited by other members.
This is disclosed in Japanese Patent Application Laid-open No. 4-175465 (1992), a construction in which the collector or intake assembly forming part of the negative pressure intake passage is disposed next to and separated by a partition wall from the independent intake pipes which communicate with each cylinder. However, in such a system, the passage from the air cleaner, which requires the largest occupied space, to the collector is placed at a position different from that of the unit including the collector and the independent intake pipes. Therefore, extra room is required, a large number of parts, such as attachment members for supporting the intake system members, are also required, and the arrangement has the disadvantage of being high in cost.